Charged particle accelerator with single or multimode operation

ABSTRACT

This invention pertains to a particle accelerator which can be made in linear, circular, helical or spiral form. It functions in one, or in a combination of modes of operation as a double betatron, double cyclotron, double traveling wave tube, or double-rotating magnetic flux device. In the double betatron mode, the particles rotate around two magnetic fluxes intertwined like two consecutive links of a chain. In the double cyclotron arrangement, the particles are accelerated at their passage between two consecutive tubes, and also between two halves of the same tube section, split longitudinally. In the traveling wave tube mode, the particles are accelerated through their energy exchange with traveling waves flowing along a coiled coil helical winding. In the arrangement with two sets of windings producing two interlinked rotating magnetic fluxes, the particles act like free electrons in the rotor of an asynchronous motor. In any one, or in any combination of these modes of operation of this particle accelerator, the particles perform a motion along a helical path, along which they cut the lines of the magnetic force of a radial, stationary, (DC excited) magnetic flux, which induces in them an electromotive force in direction of their acceleration. Normally, this particle accelerator is evacuated, but it can also be filled with a semiconductor, semimetal, or electrolyte, with the result of a considerable simplification of the device. This accelerator can be used for single, or for repeated passages of the particles through it.

United States Patent [72] Inventor Henry Greber 225 West, 80th Street,Apt. 8-D, New York, N.Y. 10024 [21] Appl. No. 801,276

[22] Filed Feb. 24, 1969 [45] Patented Nov. 2, 1971 [54] CHARGEDPARTICLE ACCELERATOR WITH SINGLE 0R MULTLMODE OPERATION 4 Claims, 9Drawing Figs.

313/63, 313/161, 328/234, 328/237 7 [51] Int. Cl 1105]! 9/02, HOSh11/00, HOSh 13/00 [50] Field 01 Search 313/63, l61;328/233,234,237

Primary Examiner-Roy Lake Assistant Examiner- Palmer C. Demeo ABSTRACT:This invention pertains to a particle accelerator which can be made inlinear, circular, helical or spiral form. It functions in one, or in acombination of modes of operation as a double betatron, doublecyclotron, double traveling wave tube, or double-rotating magnetic fluxdevice. In the double betatron mode, the particles rotate around twomagnetic fluxes intertwined like two consecutive links of a chain. Inthe double cyclotron arrangement, the particles are accelerated at theirpassage between two consecutive tubes, and also between two halves ofthe same tube section, split longitudinally. In the traveling wave tubemode, the particles are accelerated through their energy exchange withtraveling waves flowing along a coiled coil helical winding. In thearrangement with two sets of windings producing two interlinked rotatingmagnetic fluxes, the particles act like free electrons in the rotor ofan asynchronous motor. In any one, or in any combination of these modesof operation of this particle accelerator, the particles perform amotion along a helical path, along which they cut the lines of themagnetic force of a radial, stationary, (DC excited) magnetic flux,which induces in them an electromotive force in direction of theiracceleration. Normally, this particle accelerator is evacuated, but itcan also be filled with a semiconductor, semimetal, or electrolyte, withthe result of a considerable simplification of the device. Thisaccelerator can be used for single,or for repeated passages of theparticles through it.

PATENTEDunvz 1971 3,617,

INVHN'I'UR.

CHARGED PARTICLE ACCELERATOR WITH SINGLE R MULTIMODE OPERATION Thepurpose of this invention is to provide an efficient, high-power,particle accelerator capable of accelerating charged particles of anykind. Another objective is to provide a particle accelerator of smallsize and modest energy requirements, but capable of yielding chargedparticles of high kinetic energy.

These purposes are achieved by accelerating the particles along thetrack of the accelerator as well as by rotating them azimuthally inplanes perpendicular to that track, so that in effect their paths arehelical. While the particles follow such paths, they cut the magneticlines of force of a stationary radi al magnetic flux, excited with DC,which induces in them electromotive forces. This principle is maintainedin all modes of operation of this device. It can function as a doublebetatron, double cyclotron, double traveling wave tube, and as a devicewith windings producing two interlocked rotating magnetic fluxes, or inany combination of these modes. This particle accelerator can be linearof cyclic. Through deviation of the par ticles from the outlet back intothe inlet of a linear particle accelerator, it can work cyclically. Inone design modification or in the other, this particle acceleratoroperates with only moderately high voltages, so that problems ofdielectric breakdowns in containment chambers are avoided. The normallyevacuated containment chamber of the accelerator can be filled with asemiconductor, or an electrolyte, or a semimetal.

The way in which the above delineated concepts are carried out and thedesign features of the different embodiments of this invention can beseen from this specification and from the accompanying drawing.

In this drawing FIG. I is a front view of a double betatron accelerator,whose longitudinal cross section is presented in FIG. 2. In FIG. 3, isshown a longitudinal cross section of a double-cycIotron-type linearparticle accelerator. A longitudinal cross section of a double travelingwave tube particle accelerator is drawn in FIG. 4. In FIG. 5, can beseen a longitudinal cross section of a particle accelerator havingwindings producing two interlinking magnetic fluxes. The front elevationof this particle accelerator is shown in FIG. 6. FIG. 7, represents alongitudinal cross section of a particle accelerator functioning as adual traveling wave tube. A diagrammatic view of three interlinkedcyclic particle accelerators canbe seen in FIG. 8. Finally FIG. 9 showsa diagrammatic view of two interlinked cyclic particle accelerators.

In detailed consideration of FIG. 1, it can be seen that the cylindricaltube 1, of the accelerator carries winding 2, wound around the wall ofthe tube. Inside tube 1, there is another winding 3, diagrammaticallyindicated with a dash-dotted circular line. In the middle of the tube isinstalled the cylindrical winding 4, producing the stationary radialmagnetic flux. This flux passes through the bar-shaped part 5, of themagnetic circuit connecting diametrically opposite points of tube 1. Thefront view shown in FIG. 1, is taken along line A-A, indicated in FIG.2.

In the longitudinal cross section of the dual betatron particleaccelerator drawn in FIG. 2, can be seen tube 1, carrying winding 2,which is indicated diagrammatically with dashdotted lines. In this FIG.the cross sectional view of cylindrical winding 3, can be seen, as wellas that of cylindrical winding 4,

mounted on the rod-shaped part 6 of the magnetic circuit. The totalmagnetic circuit consisting of parts 1, 5, and 6, can be made offerrites, ferrites sintered with ceramics, or of ceramics. In the lattercase the magnetic core is equivalent to an air core. Winding 4, is fedfrom a source of DC indicated with the numeral 7. Similarly winding 1,is fed from a AC source 8; and AC source 9, feeds winding 3. Numeral 10,denotes a source of charged particles, such as a radioactive isotope, ora slotted cathode cooperating with a circular anode II. The potentialdifference between ring-shaped cathode l0 and anode I1 is maintainedfrom a DC potential source 12. The time variable magnetic flux inducedby winding 2, in magnetic core I, reverses the stream of particles fromthe outlet of the accelerator at anode I], to its inlet at cathode 10.If the source of charged particles 10 emanates positively chargedparticles, circular electrode 11 is, of course, charged negatively. Thepath of the charged particles is diagrammatically indicated with thedotted line 13. In actuality, the particle stream around the entire wallof tube 1.

In the longitudinal view of the dual cyclotron particle acceleratorshown in FIG. 3, the magnetic circuit consistsof tube 14, bar-shapedpart 15, and rod-shaped part 16, in complete analogy with the magneticcircuit shown in FIG. 2. The cylindrical winding 17, fed from the DCsource 18, produces a magnetic flux which flows out radially from rod 16toward tube 14, and returns via bar I5. Annular cathode l9, and circularanode 20, are connected to source 21, of DC potential. The cyclotronelectrodes consist of pairs of concentric conical tube sections: 22, 23and 24, 25, as well as 26, 27. The middle pair of concentric conicaltubes is shown in perspective in order to point out that the inner tubesection consists actually of two symmetrical parts 24, 28. Similarly,the outer tube section is made up of tube parts 25, 29. The otherconcentric conical tube sections are structured in the same way, thatis, their inner and outer tubes consist each of two symmetrical parts.It can be seen that whereas outer tube sections 23 and 27 are connectedto one terminal of AC source 30, outer tube 29 is linked to the otherterminal of the same source 30. In addition, each symmetrical part of anouter tube section, such as for example 25, 29 is connected to aseparate AC source 31. Though such source is shown only for parts 25, 29of the outer tube of the middle cyclotron electrode, it is to beunderstood that also the other parts of outer tubes 23 and 32, as wellas 27, 33 are provided with such AC sources, which are not shown inorder not to overcrowd the drawing. Dotted lines 34 and 35 indicate aconical particle beam passing through the conical double-walled tubesection, such as the space between parts 24, 28, and 25, 29. The numeral36, designates the tube segment opposite to that marked 26. Likewise,the numeral 37, labels the tube segment opposite to 23.

The magnetic circuit of the linear accelerator functioning in thetraveling wave tube mode, whose longitudinal cross section is shown inFIG. 4, consists of three parts 38, 39, 40. This magnetic circuit iscompletely analogous to these shown in FIGS. 2 and 3. Cylindricalwinding 4], fed from DC source 42, produces a stationary magnetic flux,whose lines of force flow out from rod-shaped part 40, and returnthrough parts 38, 39. The source of charged particles is exemplified asa ring shaped cathode 43, heated by the DC source 43. DC source 45maintains a potential difference between the cathode 43 and thering-shaped anode 46. The traveling wave tube winding consists of a coilhelically wound on tube 38. The convolutions 47, 48, 49 of this windingare fed from AC source 50. Dotted lines 51, 52 indicate the particlebeam.

The linear accelerator, whose longitudinal cross section is shown inFIG. 5, has a magnetic core consisting of three parts 53, 54 and 55,similar to those described in the preceding FIGS. The cylindricalwinding 56, fed from a DC source, which is not shown to avoidunnecessary repetition, produces a radial stationary magnetic flux. Aring-shaped channel 57 emanates, for example, positively chargedparticles from a radioactive isotope. These particles in the tubularbeam indicated with the dotted lines 58, 59, are attracted to thenegatively charged ring-shaped electrode 60. The source of the potentialcharging this electrode is not drawn, since it is immaterial to thisinvention. What is material is the polyphase, in this case, three-phasewindings, 61, 62, 63, connected with one of their ends to the tenninals64, 65, 66, of the threephase source, not shown, and with the other endsto the neutral point 67. These windings produce a rotating magnetic fluxcircling around the wall of the tubular core of this accelerator. Thefront view of this device, taken along line B- B is shown in FIG. 6.

In FIG. 6, it can be seen that the tubular part 54, of the magneticcircuit of this accelerator is provided with three windings 68, 69, 70,constituting a three-phase system producing a rotating magnetic flux.The three-phase potential source feeding these windings, which may bethe same as that feeding windings 61, 62, 63, of the preceding FlG., isnot shown for simplicity. Cylindrical winding 56, and part 55 of themagnetic circuit, both shown already in the foregoing, are drawn againin this FIG.

The longitudinal cross section of a linear particle acceleratorfunctioning as a dual betatron is shown in FIG. 7. Parts of the magneticcircuit of this accelerator are designated with the numerals 68, 69, 70.Cylindrical coil 71, fed from DC source 72, produces the stationaryradial flux. The cylindrical part 70 of the magnetic circuit carrieswinding 73, fed from AC source 74. This is one of the betatron windingsforcing the particles to rotate around the longitudinal axis of thisaccelerator. The other betatron winding 75, is wound around the wall oftube 68, and is fed from AC source 76. Ring-shaped channel 77, containsa source of positive particles, for example, emitted from a radioactiveisotope. These particles are attracted toward a negative ring-shapedelectrode '78. The source of potential feeding this electrode is notshown, for simplicity. Dotted lines 79, indicate the tubular stream ofpositively charged particles.

Two linear accelerators according to this invention can be used intandem. As already mentioned, any of the described accelerators can beused for cyclic operation, by reverting the particles coming out fromits outlet back to its inlet. This, however, does not preclude thedesign of this particle accelerator in circular or elliptical form, andganging up several such accelerators into one system. An example of sucha system is diagrammed in FIG. 8. There, can be seen three ellipticalparticle accelerators 80, 81, 82, combined in one system. Particlesaccelerated in one elliptical accelerator may be different than those inthe other elliptical accelerators. They are brought to collision in theinner torus 83, particularly at its points 84, 85, 86. It is importantto notice that ring 83 can be used as a retaining storage ring in whichparticles rotate without being accelerated.

In FIG. 9, two elliptical accelerators 87, 88, are combined into onesystem. The particles accelerated in this system collide in the innertorus 89, particularly at its points 90, and 91. Also torus 90 can beused for retaining particles in storage.

Either the entire particle accelerator, except its potential sources, ismounted in a vacuum chamber, or such chamber is installed within thetubular magnetic core of the device. In the latter case, the vacuumchamber is made of glass or ceramics, lightly silvered to prevent theaccumulation of static charges due to stray charged particles. This filmmust be interrupted at intervals in order not to let a current flow init. The betatron, traveling wave tube orrotating-magnetic-flux-producing windings can be connected in series orin parallel with condensers, for the purpose of creating a resonancecondition in them, and thereby large currents and consequently, largemagnetic fluxes.

A typical accelerator according to this invention is relatively short,contains only two electrodes, a negative at its entrance, and a positiveat its exit for negative particles, or electrodes of opposite polaritiesfor positive particles, and is used either for single, or for repeatedpassages of the particle bunches through it. The essential mode ofoperation of this particle accelerator is that of a dual betatron. It isprovided with two betatron windings. One creating a longitudinal, theother producing an azimuthal magnetic flux. In addition to these twowindings, the accelerator may be equipped with other windings whosefunctions will be described shortly. In its betatron mode of operation,the longitudinal magnetic flux of the accelerator causes the containedin it particles to rotate around its longitudinal axis. By doing so,they cut the lines of the stationary, DC induced magnetic force,consequently, a magnetomotive force is induced in them. Thismagnetomotive force increases the electrostatic attraction between theparticles and the electrode at the exit from the accelerator. Thiselectrode is loaded with a charge of opposite sign to that of theparticles. The azimuthal magnetic flux accelerates the particles alongthe axis of the accelerator. The same flux turns the particles aroundfrom the exit to the entrance of the accelerator for repeated passagethrough it. As known, the operation of the betatron is based on the sameprinciple as that of an ordinary transformer. The alternating primarycurrent produces a time-varying magnetic flux, which induces anelectromotive force in the charged particles. This accelerator has twosuch magnetic fluxes interlocked like two consecutive links of a chain.Both fluxes induce electromotive forces in the particles, which areinjected in pulses into the accelerator, or bunched in it. The total runof the particle through the accelerator lasts one-quarter of a cycle, sothat it hits the target with maximal velocity. At a frequency of 10 Hz.and a tube length of 100 cm; the particle velocity would be l00/4=l0'c/12, where dis, as usually, the velocity of light. This is its averagevelocity. Its maximal velocity is larger by a factor of 2, and stilllarger by the same factor taken another time due to the geometricaladdition of the equally large azimuthal velocity, and would, thereforereach one-sixth of the velocity of light. The energy gained by theparticle around one of the betatron fluxes corresponds to the voltage ofan imaginary one turn coil wound around the same flux. This voltageequals the time rate of change of this flux:

' eV=ed I /dt=amv/2 where, e is the elementary charge of the particle, Qis the magnetic flux, eVis the energy gain of the particle inelectronvolts, m is the mass of the particle, and v is its velocity,whereas a is a coversion factor leV=l.6 l0ergs. The radius of rotationr, of the particle in an azimuthal plane is given by r-=mv/Be (or givena maximal r, v, can be computed) where B, is the intensity of theazimuthal magnetic flux. The period of rotation T, of the particle inthe azimuthal plane is T-1rm/Bev is independent from r.

Two interlinked magnetic fluxes, as the ones just described, can beproduced not only by means of two betatron-type windings, but also withother kinds of windings, which can be used as a substitute, or as asupplement of the betatron winding. So, for example the two magneticfluxes can be produced with two windings similar to the ones used inelectrical rotating machines, and creating rotating magnetic fluxes.Polyphase, usually three-phase current, is used for this purpose.However, two-phase current may be practical when only single-phasehigh-frequency current is available, and the auxiliary, by degreesshifted phase current can be produced by application of capacitors orinductances. Furthermore, two interlocked magnetic fluxes can beproduced by two travelingwave-tube-type windings, wound one around thewall of the magnetic core tube, and the other wound along that wall.Conveniently, the two windings can be replaced by one, taking on theform of a coiled helix would on the magnetic core tube, as shown in FIG.4. Obviously, all these different types of windings are equivalents,which can be used either separately or together.

As the velocity of the particles approaches the speed of light the taskof the particle accelerator becomes easier. Since with its velocity alsothe mass of the particle is increased; to small increments of velocityin this range correspond large increases of energy of the particle.Besides, a beam of high velocity particles does not spread, and does notneed to be focused by means of an axial magnetic flux. Such flux iscapable of preventing the spreading of two oppositely directed beamscontaining oppositely charged particles.

The evacuated tubular space, in which the charged particles areaccelerated in the basic form of this invention, can be replaced with asemiconductor, electrolyte, or semimetal. In these media, the particlescan be accelerated to such high velocities that they are ejected fromthese bodies. The great advantage of using a semiconductor instead of anevacuated enclosure is that many difficult vacuum techniques are therebyavoided, and also a striking simplicity is achievable by thissubstitution. With semiconductors there are practically no limits to thesmallest and largest size to which a particle accelerator can be built.

As already stated, pairs of accelerators, be it linear or cyclic, withevacuated, or semiconductor, or electrolyte, or semimetal accelerationchambers can be combined into systems, such as exemplified in FIGS. 8and 9.

For large energies the practicality of the particle accelerator forspeeding up electrons is limited by their radiation losses. These,however, become negligible for heavier particles, since the radiationloss is proportional to the inverse of the fourth power of the mass ofthe particle. This fact makes it convenient to accelerate protons,deutrons and tritions, and use these particles to produce nuclearfusion. A strong proton flux produced in a system of these particleaccelerators can serve for the creation of controlled nuclear fission,without invoking the phenomenon of chain reaction. Therefore, suchfission could be carried out on the smallest scale desired. Otherapplications of this particle accelerator are: for atomic research, formedical research, diagnosis and therapy, for the production ofradioactive isotopes, hard X-rays and gamma-rays, for destructionlesstesting of materials, for sterilization, including sterilization of foodand for many other related purposes.

This invention lends itself to many modifications, variations andchanges through addition, omission or substitution or many of itscomponents, and through its adaptation to its many possibleapplications, all such changes being in the sense of this invention asdefined by the following claims.

What is claimed is:

l. A particle accelerator comprising, (a) a tubular envelope with acircular core within it and a magnetic core link connecting said tubularenvelope with said circular core, said magnetic core forming a magneticcircuit, in which a static magnetic flux is induced by means of a coilfed from a DC source, with the lines of magnetic force of said magneticflux being essentially perpendicular to said circular core, (b) twobetatron-type windings, from which one encircles the wall of saidtubular envelope, and the other forms a cylindrical coil concentric withand within said tubular envelope, (c) two sets of three-phase windings,each' set of windings layed out so as to produce a rotating magneticflux, the two magnetic fluxes being interlocked in a manner similar totwo consecutive links of a chain, with one magnetic flux rotating aroundthe wall of said tubular enclosure, and the other magnetic flux rotatingin an azimuthal plane perpendicular to the longitudinal axis of saidparticle accelerator, (d) a traveling-wave-type winding consisting of acoil helically would at the wall of said tubular enclosure, each of saidtypes of windings in combination, creates rotating magnetic fluxesaccelerating particles along the longitudinal axis of said particleaccelerator, and in azimuthal planes, perpendicular to saidaxis, and bydoing so cut the lines of the magnetic flux of said DC-excited staticflux, so that an electromotive force is induced in them, which increasestheir attraction to one of the electrodes, one of which is mounted atthe entrance, the other at the exit from said particle accelerator, thetwo electrodes being connected each to the opposite pole of a DC source,with the electrode of the polarity opposite to the polarity of thecharge carried by the accelerated particles being placed at the exitfrom said particle accelerator. f

2. A particle accelerator as described in claim 1, with the space, inwhich the particles are accelerated, filled with one of the materials ofthe semiconductors and semimetals group of materials.

3. A particle accelerator as described in claim I, with the space inwhich said particles are accelerated, occupied by an insulating tubewith double walls, with the space between these walls filled with adissociated electrolyte.

4. A particle accelerator as described in claim 1, containing cyclotronelectrodes, each consisting of pairs of concentric tube sections, eachtube being split into two halves insulated from each other, with asource of AC producing a potential difierence between two consecutivepairs of concentric tubes at the moment when a particle passes betweenthese pairs, said potential difference accelerating said particle in thedirection toward the outlet of said accelerator, with another source ofAC producing a potential difference between each pair of half tubesections which accelerate the particles in azimuthal planesperpendicular to the longitudinal axis of said particle accelerator.

1. A particle accelerator comprising, (a) a tubular envelope with acircular core within it and a magnetic core link connecting said tubularenvelope with said circular core, said magnetic core forming a magneticcircuit, in which a static magnetic flux is induced by means of a coilfed from a DC source, with the lines of magnetic force of said magneticflux being essentially perpendicular to said circular core, (b) twobetatron-type windings, from which one encircles the wall of saidtubular envelope, and the other forms a cylindrical coil concentric withand within said tubular envelope, (c) two sets of three-phase windings,each set of windings layed out so as to produce a rotating magneticflux, the two magnetic fluxes being interlocked in a manner similar totwo consecutive links of a chain, with one magnetic flux rotating aroundthe wall of said tubular enclosure, and the other magnetic flux rotatingin an azimuthal plane perpendicular to the longitudinal axis of saidparticle accelerator, (d) a traveling-wave-type winding consisting of acoil helically would at the wall of said tubular enclosure, each of saidtypes of windings in combination, creates rotating magnetic fluxesaccelerating particles along the longitudinal axis of said particleaccelerator, and in azimuthal planes perpendicular to said axis, and bydoing so cut the lines of the magnetic flux of said DC-excited staticflux, so that an electromotive force is induced in them, which increasestheir attraction to one of the electrodes, one of which is mounted atthe entrance, the other at the exit from said particle accelerator, thetwo electrodes being connected each to the opposite pole of a DC source,with the electrode of the polarity opposite to the polarity of thecharge carried by the accelerated particles being placed at the exitfrom said particle accelerator.
 2. A particle accelerator as describedin claim 1, with the space, in which the particles are accelerated,filled with one of the materials of the semiconductors and semimetalsgroup of materials.
 3. A particle accelerator as described in claim 1,with the space in which said particles are accelerated, occupied by aninsulating tube with double walls, with the space between these wallsfilled with a dissociated electrolyte.
 4. A particle accelerator asdescribed in claim 1, containing cyclotron electrodes, each consistingof pairs of concentric tube sections, each tube being split into twohalves insulated from each other, with a source of AC producing apotential difference between two consecutive pairs of concentric tubesat the moment when a particle passes between these pairs, said potentialdifference accelerating said particle in the direction toward the outletof said accelerator, with another source of AC producing a potentialdifference between each pair of half tube sections which accelerate theparticles in azimuthal planes perpendicular to the longitudinal axis ofsaid particle accelerator.